Cell cycle Flashcards
why is the cell cycle so highly conserved
it is an extremely fundamental process to life. altering it would likely lead to the cells death
what are the stages of the cell cycle and what happens during each
G1: protein synthesis in preparation for S phase
S: sister chromatids are made
G2: protein synthesis in preparation for M phase
M: mitosis occurs
what are the three checkpoints in the cell cycle
G1/S phase checkpoint
G2/M phase checkpoint
Spindle fibre assembly checkpoint (SAC)
what are the three core molecules responsible for regulating the cell cycle
cyclins, cyclin-dependant kinases, ubiquitin-protease ligases
what are cyclin dependant kinases (CDKs)
CDKs are responsible for phosphorylating molecules that triggers a cascade within the cell cycle to take place. they are only active when cyclin is bound to them.
Different CDKs are active during different parts of the cell cycle.
what is cyclin
cyclin is the molecule that binds to CDKs to activate them. whilst the concentration of CDs remains constant throughout the cell cycle, cyclin concentrations fluctuate, regulating the process.
what are the different CDK-cyclin complexes and what do they do
G1-CDKs: promote entry into the cell cycle
G1/S-CDKs: promotes entry into the cell cycle as well as the progression into the S-phase
S-CDKs: trigger the synthesis of DNA in the S phase
M-CDKs: initiate the events of mitosis
what are ubiquitin protein ligases and why are they important in the cell cycle
ubiquitin protein ligases mark proteins for degredation by tagging them with ubiquitin. By tagging cyclin with ubiquitin, the CDKs will be deactivated.
This is crucial in the cell cycle as it will not be able to progress though each phase if the previous CDK is not deactivated.
how does the cell exit the M phase
ubiquitin ligase proteases mark the cyclin in the M-phase CDKs cyclin complex. This deactivates the CDK and lets the cell cycle restart.
what is cyclin-B and why is it important
cyclin-B activates the M-phases CDKs, initiating mitosis. It is very important since the M-phase can not complete itself if the M-CDKs are still activated, so cyclin B must be degraded in order to complete the cell cycle.
other than cyclin, what is another method by which CDKs are regulated
in order for a CDK-cyclin complex to be activated it must be phosphorylated. this is done through an inhibition-activation approach.
what is MPF
Mitosis Producing Factor (MPF) is the effector molecule responsible for triggering the M phase. without it, the cell can not leave the G2 phase and begin mitosis.
what is APC/C
APC is a type of ubiquitin protease ligase which degrades cyclin B. this is important because it allows the cell to exit the M phase.
what are the residues on a CDK that get phosphorylated during its activation
Y15 and T161
(inhibition-activation)
what is MPF made up of
cyclin B and Cyclin Dependant Kinases
